Carbon nanotubes might be microscopic -- they're 100,000 times smaller than a human hair -- but the innovative material could have major health and safety impacts.

From detecting an oncoming asthma attack to sensing the levels of oxygen inside mines, carbon nanotubes could lead to a number of new technologies. I spoke recently with Alexander Star, an assistant professor of chemistry at the University of Pittsburgh and a 2010 Outstanding New Environmental Scientist, about the possibilities of carbon nanotubes.

What are carbon nanotubes?

Carbon nanotubes are a relatively new material which started to be used maybe 20 years ago. It is used more and more because of its excellent mechanical properties. Carbon nanotubes are typically very light and very strong. They could be 50 times stronger than steel, and yet they are light and flexible. That makes carbon nanotubes the ideal material to reinforce many composites.

You can find carbon nanotubes in many commercial applications for reinforcement of composite materials. That would include sports equipment, [such as] tennis rackets. There is a lot of manufacturing going on to scale up the production of carbon nanotubes. There are many big players producing carbon nanotubes. That's only going to increase.

What does your work with carbon nanotubes entail?

We work particularly on using carbon nanotubes for making sensors and energy conversion devices, [such as] fuel cells. Carbon nanotubes can be used as the catalyst support for electrodes on fuel cells. Carbon nanotubes can be used as excellent transducers for sensors. That's one of the main applications.

Coming back to the increased production of the nanotubes, we're very interested to find out whether certain nanotubes are toxic and what would make nanotubes biodegradable. We anticipate the production of nanotubes will be increased over time. They're going to end up in many commercial products, so the impact of carbon nanotubes on the environment is very important.

What's known about how nanotubes affect people and the environment?

There is a very active area of research related to the toxicity of the nanotubes. Carbon nanotubes were compared to asbestos for their negative impact on lung tissue if they're inhaled. The results from the literature indicate that they have toxic effects, but there is no agreement of which particular types of nanotubes can cause that effect. People are trying to understand what would make nanotubes toxic. There are some conditions under which they don't exhibit these negative effects.

If carbon nanotubes are deemed safe, what are some potential technologies that could use them?

We've worked mostly on sensors. For these applications, we don't think there will be any negative affect of nanotubes. We want to use very small amounts of nanotubes and incorporate them into silicon wafers for the circuitry of the sensors.

We developed sensors for asthma. People with asthma have elevated levels of nitric oxide in their breath compared to healthy people. By measuring levels of nitric oxide in one's breath, we can predict the level of inflammation and when these asthma attacks can happen. This type of sensing has diagnostic value. One can then take a medication to prevent the asthma attack from happening. Because of their small size -- each nanotube is 100,000 times smaller than a human hair -- nanotubes can make very small wires that can be sensitive to many gasses. In this case, nitric oxide is one of these gasses.

In addition to nitric oxide, we were able to detect oxygen. The detection of oxygen is very important, not just in the medical field, but in personal protection. People working in confined spaces, such as miners, need to know the levels of oxygen. If you can make the sensors small enough and light enough for people to carry them around or, ideally, incorporated in the uniforms of the workers, then it can be a good approach for personal safety. Carbon nanotubes are the ideal material for this purpose because they are extremely small. They allow us to make very tiny sensors. They don't take much power. A watch battery would be enough to run them for years.

How did you end up in this field?

Carbon nanotubes are a new material and I was exposed to them when I did my post-doctoral work at UCLA. We were trying to find out the chemistry of carbon nanotubes. During my post-doctoral work we developed certain ways to functionalize nanotubes while preserving their properties. That was quite useful for developing sensing.

What's next for you and this work?

In the future I can envision having one sensor device made of the nanotubes, but functionalized for all those important chemicals to detect. We want to be able to detect even more chemicals than we showed so far.

Thank You

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